Variable pitch propeller



June 19, 1951 H. MAGILL VARIABLE FITCH PROPELLER Filed Dec. 50, 1943 NNNNNN .BY Wlan-ry' A11-tjrs Patented June 19, 1951 f- UNITED STATES PATENTOFFICE VARIABLE FITCH PROPELLER Herbert L. Magill, Chicago, Ill.Application December 30, 1943, Serial No. 516,258

Fig. 1 is a vertical sectional view, shown more or lessdiagrammatically, showing a preferred embodiment of my invention, withparts of the View being broken away for clarification.

Fig. 2 is a section of a detail construction of the friction deviceshown in Fig. 1.

The propeller I5 is shown as an aircraft propeller, but could be apropeller for use in any Vfluid medium. It is propelled in any suitablemanner, as for example, by reaction jets, located at or near the tips ofthe propeller blades on the trailing edges thereof, and through whichthe exhaust from a gas pressure generator I9 is discharged. Thepropeller blades are so mounted that their pitch is automatically ormanually changed as desired, as the plane varies in altitudes. At lowaltitudes the plane is propelled principally by the forced rotation ofthe blades I5 by the reaction jets, but at high altitudes the plane ispropelled by the reaction jets on the propeller blades, augmented, ifnecessary, by additional reaction fjets.

Mechanism for varying the pitch of propeller Y blades Attached to andextending forwardly from the pressure generator is a mounting or housing2 I2, within which is rotatably mounted the propeller shaft 2I3.Suitable anti-friction bearings 2I4,

ing 2I2. The propeller I5 is attached to the hub 221i in such a mannerthat the propeller 7 Claims. (Cl. T10-135.4)

v4:0 2 I5, are provided for this shaft within the housblades may bevaried in pitch, as will now be described.

Attached to the forward end of the propeller shaft 2I3 is a hub 224,within which the inner blades 22D will be rotated about theirlongitudinal axes, due to the meshing of the gear 221 with the gears 22don the inner ends of the propeller blades.

Each of the propeller blades is provided with a conduit 222, whichextends longitudinally of the blades and have their inner ends enlarged,as at 222e, and through which the exploded gases from the pressuregenerator I9 are conducted to the reaction jet nozzles located on therear or trailing edges of the propeller blades, as previously dsecribed.

The propeller shaft 2 I3 is hollow, and the tubular conduit Il8 extendsaxially therethrough. At its rear end the tubular conduit |18 is rigidlyconnected to the propeller shaft by a bracket or supporting member 2 I6.i

The forward end of the tubular conduit I'I8 is provided with branchconduits, one for each propeller blade. Where the propeller has but twoblades, as shown in Fig. 1, the conduit Il is bifurcated, or terminatesin a T-shaped hollow member 2I3, the arms 2I9 of which extend laterallyinto the enlarged ends of conduits 22| and 222, extending lengthwise ofthe propeller blades 220, and through which the exploded gases from'thepressure generator I9 are conducted to the reaction jet nozzles locatedon the outer trailing edges of the propeller blades.

In an airplane having means for propelling the same either by employingreaction jets or by rotating propellers, it is desirable that theconstruction be such that the change from one means of propulsion to theother may be accomplished by either, and the pitch of the propellerblades be controllable when being propelled by rotating Propellers tomaintain the rotation of the propellers at a constant speed by changingthe pitch of the propeller blades as the density of the atmosphere mayvary by reason of a change in altitude of the aircraft in ight toprovide the most efficient pitch for the propeller blades consistentVwith the power being applied and the atmospheric density.

For instance, in ascending or descending under normal conditions, thechange from propulsion by reaction jets to propulsion by rotatingpropel- 1ers, or vice versa, and the change of pitch of the blades ofthe propeller during such time that they supply the propelling means isdesirable to be accomplished at the will of the pilot, and preferably byautomatically operated mechanism.

In the present invention the change is made by merely changing the pitchof the blades. Means are provided for. changing and for also reversing 3the pitch of the blades, and there are times when it is highly desirablethat this change pitch mechanism be manually controlled, as, forinstance, in dive bombing. When nearing the limit of a dive underbombing conditions the pitch of the blades may be manually controlled tocause them to function as brakes for a brief period of time in order torelieve strains on the dirigible mechanism of the plane. In reversingthe pitch of the.-

blades for braking action to retard forward movement of the aircraft,there is a reversal in the direction of the air-screw effect but thepropeller continues to rotate in the same direction.

The mechanism for varying the pitch of the propeller blades comprises ahollow cylindrical shaft 22 3, concentrically mounted within thepropeller shaft 2l3, and is relatively rotatable therein, as by means ofthe anti-friction bearings 225a and 225. Mounted on the outer end of theshaft 223 is the bevel gear 227 that engages bevel gears 22S and 226a onthe inner ends of the propeller blades for rotating the blades, asdescribed above. lThe hollow shaft 223 has a spiral thread or gear 2239-thereon, which is engaged by an internal spiral groove in a sleeve 223i.The sleeve 223b is slidably mounted within the propeller shaft 2l3. Anouter sleeve 22%a is slidably mounted on the drive shaft 213. These twosleeves are connected to slide together along the drive shaft, but areprevented from turning on said shaft by a plurality of blocks 22ilb,which are slidably mounted in slots 22Bc in the wall of the propellershaft 2I3. Screws 22T!d hold the sleeves and blocks together so thatthey may slide as a unit longitudinally of the shaft 223.

The means for moving the threaded sleeve and associated parts along theshaft 223 comprises a yoke or depending arms 220e, pivotally mounted, asat 22if, and having their lower ends at opposite sides of the hollowshaft bifurcated, as at 225g, engaging blocks 22Eih pivoted to an outerring member 22]i at opposite sides thereof, and which in turn surroundsthe sleeve 220a. Antifriction bearings 2205 are provided between thering 226i and the sleeve 226e, and thus the sleeve 22a, propeller shaft2|3, and hollow shaft 223 normally turn together, while the ring 220iremains stationary so long as the arms 22]e remain stationary.

It will thus be seen that when the arms 226e are turned about the pivot220f the ring 22Eii is moved along the propeller` shaft, and. due to theball bearing connection and construction the sleeve 226e, and with itthe sleeve 223', are moved along the hollow shaft 223, thus rotating thelatter for rotating the gear 221, which in turn rotates the gears 226and 2253a for varying the pitch of the propeller blades.

The means for automatically and for manually rotating the arm 22]e willnow be described.

The arm 220e is extended beyond its pivot 22Df, and is provided with atoothed quadrant 220k, which is adapted to be engaged by a self-lockingworm 2201 on the shaft of a reversible motor 22cm, adapted to oscillatethe arm 22%e in either direction. The operation of the motor iscontrolled by an automatic switch mechanism I, or by a manually operatedswitch mechanism 2 (Fig. l). The automatic switch mechanism l comprisesa housing 2X, which is rigidly connected to the housing 2| 2 and hasrotatably mounted therein a gear 3 which meshes with a gear 4` rigidlymounted on the propeller shaft 2 I3. The gear 3 is rigidly mounted on ashaft 5, and a governor E is also mounted on this shaft 5.

Automatic governor for pitch control The governor B, which is of theusual centrifugal type, comprises a collar 7, rigidly connected to theshaft 5 and rotatable therewith. This collar has connected thereto theusual centrifugal ball and link connection 8, which is connected to asleeve 9 slidable along the shaft 5. A spring le is mounted on the shaft5 between the collar l and sleeve S for normally holding the latter inits outermost position. Connected to the sleeve 9, as by means of a ballbearing 2a, is a switch operating shaft 3a, having rack teeth 48Lthereon. The shaft 3a is free to move horizontally through a cylindricalcasing 2y, which is slidably supported at its inner end 2m in a bearingsupport 2k rigidly attached to the open end of the housing 2X. Thebearing support 2k has an extension 2S, to which are attached the twofixed elements 4m and lb of a multiple switch 6a.

The casing 2y has extensions. 23, to which is attached the movableelement 5a ofv a multiple switch 6a extending outwardly through the slot2n in the extension 2s of the bearing support 2k, and is yieldingly heldin adjusted position by a spiral toothed gear 2P, rotatably mounted in aspring-pressed block 2q slidably mounted in a bore 2f in the lateralextension 2t of the casing 2y. The spring compression is controlled bythe threaded bolt 2W. The gear 2D, meshing with the rack teeth 4, holdsthe casing 2y in adjusted position without offering too much frictionalresistance to the endwise movement of the shaft 3a.

The switch operating shaft 3.a doesnot rotate but is adapted to be movedlongitudinally of the shaft 5 by the centrifugal governor mechanism 6.Likewise the casing 2y, which is slidably mounted on the shaft 3a, doesnot rotate but is adapted to be moved in either direction by thefrictional contact between the spiral toothed gear 2p and the rack teethlia by a corresponding movement of the shaft 3g until the movableelement 5a contacts either of the Xed elements 4m or 4b o-f the multipleswitch 5a. After such contact the Sleeve 2y is prevented from movingfurther in that direction, but the shaft 3a may continue to move in thesame direction if the speed of the governor continues to increase ordecrease, as the'case may be.

The movable element 5a of the switch (ia is provided with a pair ofcontact members 'la and 821. The contact member 3a, when at one extremeposition, is adapted to engage a pair of contact members ib, 2b, and theContact member la is adapted to engage the contact member 31U on thefixed portion lib of the switch 5a, When moved in the opposite directionthe terminal 8a is adapted to engage the two terminals 5b, 6b, of thefixed portion of the switch, and the terminal 'in will Contact theterminal 'lb of the fixed portion of the switch and make electricalconnections therewith.

Elcctric circuits for change pitch mechanism When the plane passes fromone density of the atmosphere to another, as when ascending, it passesinto rare atmosphere, the propeller, having less resistance due 'to therarity of the atmosphere, will tend to move faster, and this will causethe balls of the governor 2 to move out by centrifugal force, causingthe sleeve 9 to move to the left in Fig. l, and this in turn will movethe sleeve 3R, and with it the movable element 5a of the switch, therebybringing the terminals la, 821, in contact with the terminals lb, and5b, 6b, respectively.

Y y `When these connections are made the electric current from asuitable source of electrical energy, as the battery 8b, will cause themotor 220m to rotate in one direction for increasing the pitch of theblades, as will presently be described.

In passing into a denser atmosphere the reverse will be true, and theelectrical connections will be changed so that the motor will be rotatedin the opposite direction for decreasing the pitch of the propellerblades. The motor employed is shunt wound, and the reversal of the motoris effected by reversing the field which is secured by reversing theflow of current through the shunt winding from the battery.

Assuming that the movable element 5EL of the switch 6a has been moved tothe left in Fig. l and made electrical connections with the terminals onthe fixed portion of the switch, and assuming that the blade switch9kb/which is connected to the terminals i0, 2 and 3, is now in contactwith the `terminals 4c, 5C and 6G, the current may be traced as follows:

From the battery 8b through the switch 350 to the `main line B, terminal8a, where it divides, one portion passes to terminal 6b, through aconductor 3e to the terminal ic across the switch to the terminal IC,and from the terminal i@ through the conductor ic to the terminal 50 ofone of the brushes of the motor, and thence returning through the otherbrush and terminal 9c of the motor, thence through the conductor Id,back through the main line A to the ground, as at 2d.

The other portion of the current passes from the terminal 8a to theterminal 5b through a conductor to the terminals 6c and 3c of the switch9b through the conductor 3d to the ter. minal 3d of the field winding,thence through the eld to the other eld terminal 5d, through conductorSd, terminal 2c, switch 9b, terminal 5c, thence through terminals lb,la, and nally through conductor 6g and conduit A to the ground 2d. Therotation of the motor causes the arms 22|)e to rotate in one direction,which in turn moves the sleeve 223b along the cylindrical shaft 223,thus rotating the cylindrical shaft 223 independently of the propellershaft 2 I3 for causing a change in the pitch of the propeller blades.

The motor 22E!m continues to operate and move the sleeve 223b, causingthe pitch of the propeller blades to continuously increase until theadded resistance to the rotation of the propeller causes it to decreaseits speed. As the speed decreases the governor 6 acts to move the shaftila to the right, carrying with it the casing 2y and the attachedmovable element 5a, breaking the electrical contact between itsterminals 8a and ia and the terminals 6b, 5b and lb, respectively, andstopping the motor 220m and leaving the blades of the propeller lockedin a fixed position, by the self -locking worm 2261, with the toothedquadrant 223k of the arms 220e.

When the switch member 5a is moved to the right in Fig. l, as when theplane moves into denser air, and the speed of the propeller decreasesdue to this denser air, the contacts are made at the opposite side ofthe switch, thus reversing the current through the field and reversingthe motor, Which in turn lowers the pitch of the blades through thegears 226, 221 and 226e. The circuit may now be traced as follows:

From the battery 8b through the main line B to the switch terminal 8a,terminal lb, conductor le, terminal 5, through the blade of the switch9b to terminal 2C, conductor 6d to the terminal 5d of the field-1K1,back throughthe terminal 4d of 6. the field,'conductor 3d, terminal 3c,blade of the switch 9b to the terminal 60, thence through the conductor2e, terminal 3b, terminal 1a, conductor 6g, through the main line A tothe ground, thus reversing the motor.

The current through the brushes of the motor may be traced as follows:

From the battery 8b through the switch 350 to main line B, to theterminal 8a, through the ter-- minal 2b, conductor 3e to the terminal4C, through the blad-e of the switch 9b to the terminal ic, con-v ductorlc, terminal 8c of the motor to the terminal 9C of the motor, conductorld, and through theA main line A to the ground.

Thus it will be seen that when the propellers are controlled to beoperated at any rotational` speed within its speed range by suitablemanipu lation of a control valve or element, the mech-y anism justdescribed will act to automatically cause the pitch of the propellerblades to increaseuntil the amount of power applied to the pro-r pelleris no longer able to increase its rotational. speed against theincreasing pitch of its blades, and will then act to lock the blades ina position of pitch most efficient for the maximum rota-- tional speedof the propeller with the amount of power being applied.

Likewise, with the propellers operating as above described, the motor22@m will be caused to rotate in such direction as to automaticallyincrease the pitch of the blades should the aircraft ascend, or decreasethe pitch of the blades as the aircraft descends, to maintain therotational speed of the propeller at a constant through variation of theatmospheric density.

The main line B is in series with the switch 350 (Fig. 1), so that whenthe ignition circuit for the pressure generator I9 is open the circuitfor the motor 22Bm will likewise open, and the motor will not function.

It is significant that the automatic governor for propeller pitchcontrol does not provide some specified pitch angle for a given numberof R. P. M s of the propeller, but rather introduces another variable sothat the governing means responds not only to changes in the power inputto the propeller, but also thc fluid resistance to rotation of thepropeller to provide a pitch for 'the propeller which effectivelyabsorbs the power being applied by said power means to rotate thepropeller.

Manual control for changing pitch of propeller blades When it is desiredto vary the pitch of the propeller blades manually, the switch 9b ismoved over to the opposite side in contact with the terminals 4e, 5e and6e, so that the automatic operation of the switch mechanism for themotor 226m is ineffective. The switch mechanism 2 can then be operatedmanually so as to vary the pitch of the propeller blades. 'The switchmechanism 2 comprises a casing le, having a shaft Se extendingtherethrough, on which is slidably mounted a sleeve 9E having gear teethlf on one side thereof. A lever 2f, pivoted in the casing, as at 3f, andhaving gear teeth df, is provided for shifting the sleeve. The sleeve isnormally held in neutral orl rcentral position by springs 5f and 5f,which en gage on opposite sides of the sleeve se, as clearly shown inFig. 5 of the drawing. Rigidly attached to the sleeve Se is the movableelement if of a. switch, which is adapted to contact the stationtrymembers 8f' Sf, at opposite sides of the mov-- able element'if of theswitch.

Since the switch 2 is constructed like the switch l, it is not thoughtnecessary to repeat the description. It is believed to be obvious howthe circuits may be traced, since they are similar to those involvingthe switch 5a, and consequently the tracing of the currents is notrepeated.

It is though from the foregoing, taken in connection with theaccompanying drawings, that the construction and operation of my devicewill be apparent to those skilled in the art, and that i changes insize, shape, proportion or detail may be made without departing from thespirit and scope of the appended claims.

i claim as my invention:

l. In an aircraft, a propeller having blades, reaction jets mounted onthe propeller blades for normally rotating the propeller as a primarypropulsion means for the aircraft, means to automatically vary the pitchof said blades to compensate for changes in air speed and barometricpressure, and means to reverse the pitch of the blades independently ofsaid automatic means thereby to reverse the thrust of the propeller.

2. A propulsion device for use in fluid mediums, said device comprisinga bladed variable pitch propeller, power means to rotate said propeller,a mechanism for altering the pitch of the propeller, and automatic meansresponsive to changes in the power input to said propeller and to theiiuid resistance to rotation of said propeller 5 for operating saidmechanism to provide a pitch for the propeller which effectively absorbsand balances the power being applied by said power means to rotate saidpropeller, said automatic means comprising a first means that varies inaccordance with the speed of the propeller, a second means operativelyassociated with said pitch altering mechanism and responsive to aninitial variation in said iirst means for eiiecting a progressive changein pitch in said propeller in a direction that will oppose the change ofspeed causing variation in said first means, said second means includinga third means providing a variable coupling between the first and secondmeans for continuing said progressive change in pitch until finalstabilization of the pitch and speed of the propeller has beenestablished for the changed conditions under which the propeller isbeing rotated.

3. A propulsion device according to claim 2, in combination with meansfor selectively varying the pitch of the propeller1 by manual control.

4. A propulsion device according to claim 2, in combination with manualmeans for selectively varying the pitch of the propeller, means forreversing the pitch of said propeller whereby the propeller acts as abrake, and means to control the pitch of said propeller blades when inreverse pitch by said manual means.

5. A propulsion device for use in aircraft, said device comprising abladed variable pitch propeller, power means to rotate said propeller, aself-adjusting governor mechanism responsive to the speed of rotation ofsaid propeller as it may be affected by variations of power input', airspeed, and barometric pressure to control and select the rotating speedand pitch of said propeller, said mechanism comprising a governorresponsive to the rotation speed of the propeller, an arm operativelyconnected to said governor and having longitudinal movement in responseto changes in the speed or rotation of the propeller, a contact memberprojecting from one side of said arm and movable with respect to saidarm longitudinally, means associated with the arm dll and contact memberto present a resistance to movement of said member with respect to saidarm, a pair of contacts positioned to either side of said member andspaced therefrom, electrically controlled means adapted to vary thepitch of the blades of said propeller, electric circuits connecting saidlast-mentioned means, said Contact member, and said contacts whereby anincrease in speed of rotation of said propeller will move said memberagainst one of said contacts to complete a circuit through saidlast-mentioned means to increase the pitch of said propeller until thespeed of rotation of the propeller becomes stabilized by the saidincrease in pitch, while a decrease in the speed of rotation of saidpropeller will move said member against the other of said contacts tocomplete a circuit through the said last-mentioned means to decrease thepitch of the propeller blades until the speed of rotation of thepropeller becomes stabilized by the said decrease in pitch, whereby aproper rotating speed and blade pitch is automatically selected toabsorb and balance any given power input applied to rotate the propellerand compensate for changes of air speed and barometric pressure.

6. A propulsion device for use in iiuid mediums, said device comprisinga bladed variable-pitch propeller, power means to rotate the propeller,pitch adjusting means for varying the pitch of the propeller,v and agoverning device automati' cally responsive to changes in speed ofrotation of said propeller for operating said pitch adjusting means toeffect a combination of pitch setting and speed of propeller rotation toeffectively absorb and balance the power being applied by the powermeans to rotate the propeller, said governing device including a firstpart movable a'long a given path with its position on said pathdetermined bj the speed of rotation of the propeller, a second partslidably mounted with resp-ect to said first part and movable therewithunless restrained from such movement, a third part adjacent said pathand relatively xed against movement, and a centering device includingtwo spaced arms carried by one of said two last-named parts, and a thirdarm extendingl between said two spaced arms and carried by the other ofsaid two last-named parts, and means operative to change the pitch ofthe propeller in one direction when said third arm makes contact withone or the two spaced arms, and to change the pitch of the propeller inthe other direction when the third arm makes contact with the other ofsaid two spaced arms, said second part being movable relative to thei'lrst part to av new position with respect thereto whenever thecooperating arms of the centering device make contact with apredetermined minimum pressure.

7. A propulsion device for use in fluid mediums, said device comprisinga bladed variable-pitch propeller, power means to rotate the propeller,pitch adjusting means for varying the pitch of the propeller, and agoverning device automatically responsive to changes in speed ofrotation of said propeller for operating said pitch adjusting meansftoeiiect a combination of pitch setting and speed of propeller rotation toeffectively absorb and balance the power being applied by the powermeans to rotate the propeller, said governing device including a firstpart movable along a given path with its position on said pathdetermined.- by theA speed of rotation of the propeller, ay second partslidably mountedl with 9 respect to said rst part and normally movabletherewith but capable of relative movement with respect to the rst part,stabilizing meansfor shifting said second part with respect to saidfirst part in response to excessive movement of said first part, saidstabilizing means being operatively connected to said pitch-adjustingmechanism to eiect a change in pitch in a direction that tends to resistthe change in speed of rotation that caused the movement of the rstpart, whereby said second part establishes a new position with respectto the rst part and the pitch and speed of the propeller areautomatically adjusted to values that effectively absorb and balance thepower input applied to the power means for rotating the propeller.

HERBERT L. MAGILL.

REFERENCES CITED The following references are of record in the file ofthis patent:

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